Comparative molecular phylogeography of two Xenopus species, X.
gilli and X. laevis, in the south-western Cape Province, South
Africa.

Evans BJ, Morales JC, Picker MD, Kelley DB, Melnick DJ

Xenopus gilli is a vulnerable anuran with a patchy distribution
along the south-western coast of the Cape Province, South Africa.
This species is sympatric with Xenopus laevis laevis, a widespread
relative found over much of southern Africa. We examined the
molecular phylogeography and population structure of the contact zone
between these species to obtain information about historical
biogeography and conservation management of this region. Analyses of
the distribution, frequency, and cladistic and phenetic relationships
among mitochondrial DNA haplotypes indicate that population
subdivision is present in both taxa but that long-term isolation of
sets of populations has occurred in X. gilli only. Haplotype and
nucleotide diversity are also considerably higher within and among X.
gilli ponds than X. l. laevis ponds in this region. We attribute the
genetic segregation of X. gilli populations to ancient habitat
fragmentation by ocean transgression into X. gilli habitat and to
continued habitat alteration by human activity. The lower level of
genetic diversity in X. L. laevis in this region is likely a result
of a recent arrival of this taxon to the south-western Cape region
relative to X. gilli. Population structure in X. l. laevis may be a
result of isolation by distance. Clear evidence exists for at least
two management units within X. gilli and strongly supports the
establishment of protective measures east of False Bay in order to
conserve a substantial portion of this species' extant genetic
diversity.